1. Technical Field
The present disclosure generally relates to flow control assemblies for fluid systems, and more particularly, to wafer check valve assemblies for piping systems.
2. Background Art
Flow control assemblies for use in fluid systems are known. For example, assemblies utilizing flow control devices (e.g., valves) in fluid systems (e.g., piping systems) have been developed. Flow control assemblies are useful in a myriad of different environments for commercial and industrial applications.
In general, wafer check valves are a type of flow control device and usually include a body component, a disc or flapper component, a means to attach the disc component to the body component, and a seal or seat. These valves typically also include a hinge or shaft, which may be an integral feature of the disc component, or may be a separate component, which for example, is inserted through the disc component and allows the disc to rotate on the shaft. Disc components and shafts are commonly attached to (or retained within) the body of the valve via various means (e.g., via fasteners, retainer rings, threaded bushings, pins, welding, etc.), depending on the design and/or materials of construction of the valve.
One primary purpose of wafer check valves is to prevent (“check”) back flow, or reversal of flow in piping systems. This checking action may be necessary, for example, when used on the discharge side of a pump, to prevent drainage of a system upon pump shutoff, or if used on the suction side of a pump, to retain “prime” in the system. In general, the field of wafer check valves has a long history with many types of designs and materials of construction. Wafer check valves are sometimes referred to as, or included as a sub-class of valves known as, swing check valves. While metal wafer check valves have generally dominated the field for over 100 years, thermoplastic wafer check valves have also been introduced within the past few decades.
Wafer check valves are typically narrow profile (short length) valves with minimal overall thickness. The body of these valves generally resembles a wafer or a disc, thus the name wafer check valve. These valves are typically installed in systems for at least two primary reasons: first, wafer check valves are installed where space is a premium—their narrow profile generally allows installation in tight spaces; and second, due to the narrow profile and minimum amount of material needed for their construction, these valves are typically lower cost than alternatives such as swing check valves or ball check valves.
In general, wafer check valves are uni-directional and are installed into piping systems between two flanges. Wafer check valves are typically designed to operate in response to the force of flow of fluids. They are also typically dependent upon gravity and/or fluid momentum to close and open. For example, for a system at rest, with the wafer check valve installed in a vertical pipe installation, the weight of the water column above the valve acts on the disc of the valve, holding it in the closed position. Once forward flow in the system is started, the disc component of the wafer check valve opens in response to the pressure and flow generated by the pump and allows flow through the system. Upon pump shutdown, gravity overcomes the forward momentum of the fluid and the fluid reverses its direction of flow. The disc component of the wafer check valve rides the column of water downward until it reaches the closed position, at which point the hydraulic head generated by the weight of the water column above the valve acts on the valve seat, and a seal is generated, whereby, no, or minimal, additional fluid is allowed past the disc component.
Wafer check valves are also installed in piping systems where the general orientation of the pipe is horizontal. In these installations, for most conventional wafer check valves, the use of a spring (typically a torsion spring, but could also be a compression or other spring) attached to the disc component is known to be typically required to bias the disc component toward the closed position, such that when the system is shut off and flow reversal occurs, the spring will move the disc component toward the closed position until sufficient hydraulic head can be generated to effect a seal. Other devices such as counterweights and/or externally mounted springs attached to the shaft of the valve are known in the art for the purpose of assisting wafer check valves to affect a seal when installed in the horizontal orientation, as well as to dampen the response of the disc component upon system startup. In general, these devices can typically only be used where the shaft of the valve extends through the walls of the body of the valve.
There are several issues, flaws and/or shortcomings with prior art designs. First, wafer check valves are generally notorious for their reduced flow port area (i.e., restricted flow). Ports are typically as little as 40% of the open area of the adjoining pipe, effectively creating a nozzle through the port of the wafer check valve.
Additionally, many wafer check valves require the use of a spacer or spool piece on the downstream side of the valve to allow the disc to open to its full extent, especially in piping systems greater than schedule 40. Typically, if spacers are not used, the rotation of the disc may be restricted, which further restricts the flow of fluid through the valve. The spacer is a general nuisance for several reasons: first, the requirement for spacers is often not anticipated nor understood by users; second, installation becomes more difficult, as another independent component must be handled and managed while attempting to install the valve and spacer between two flanges; third, the actual space in a system required to properly install wafer check valves (with spacers) is often underestimated, requiring last minute system design adjustments, sometimes additional cost, and/or compromising system performance by using the wafer check valve under less than ideal installation conditions (e.g., without a spacer), resulting in restricted flow in the system.
Moreover, installation of valves without spacers can result in the disc striking the inside wall of the adjoining flange or pipe. This can result in restricted opening of the disc, as well as damage to the disc, and possibly even failure of the disc.
Furthermore and typically with respect to thermoplastic wafer check valves, the disc to shaft transition is often the weakest link of the valve, resulting in failure of the disc due to rapid flow reversal and the associated impact loading of the disc. Additionally (and also typically with respect to thermoplastic wafer check valves), the discs of existing prior art valves are generally retained in the body using plastic fasteners, press-fit buttons or the like, or special clips. These methods typically rely, to some extent, on the proper assembly of the valve between the two adjoining flanges to assist the retention means, whereas, improper installation between the flanges (i.e., misalignment) can result in one, or both, of the retainers coming loose and allowing the disc to dislodge from the assembly.
Furthermore, conventional thermoplastic wafer check valve designs typically rely on the installer to ensure proper compression of the valve, especially the body, when the flange bolts are tightened. Excessive torque, improper bolt tightening sequence, and/or misalignment can all result in deficiencies in valve performance. By contrast, due to the differences in the strength of metal and plastic materials, metal valves are generally not as sensitive to factors associated with installation as are thermoplastic valves.
Moreover, as a result of the generally thin profile of the bodies of conventional wafer check valves and by the necessity of maintaining a narrow face-to-face profile, the seat area is often placed on a plane parallel to the front and back faces of the valve body. When installed in piping systems that are horizontal, the disc component of these valves typically hangs straight down and generally cannot render any mechanical sealing advantage from gravitational forces, thereby typically requiring the assistance of a spring to return to the closed and seated position once flow in the system terminates.
Thus, despite efforts to date, a need remains for improved systems/designs for wafer check valve assemblies for fluid systems. These and other inefficiencies and opportunities for improvement are addressed and/or overcome by the systems, assemblies and methods of the present disclosure.